Fiber optic cable

ABSTRACT

A fiber optic cable includes an optical fiber, a strength layer surrounding the optical fiber, and an outer jacket surrounding the strength layer. The strength layer includes a matrix material in which is integrated a plurality of reinforcing fibers. A fiber optic cable includes an optical fiber, a strength layer, a first electrical conductor affixed to an outer surface of the strength layer, a second electrical conductor affixed to the outer surface of the strength layer, and an outer jacket. The strength layer includes a polymeric material in which is embedded a plurality of reinforcing fibers. A method of manufacturing a fiber optic cable includes mixing a base material in an extruder. A strength layer is formed about an optical fiber. The strength layer includes a polymeric film with embedded reinforcing fibers disposed in the film. The base material is extruded through an extrusion die to form an outer jacket.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 17/080,168,filed Oct. 26, 2020, which is a continuation of application Ser. No.15/707,492, filed Sep. 18, 2017, now U.S. Pat. No. 10,816,744, which isa continuation of application Ser. No. 15/148,103, filed May 6, 2016,now abandoned, which is a continuation of application Ser. No.14/556,805, filed Dec. 1, 2014, now U.S. Pat. No. 9,335,503, which is acontinuation of application Ser. No. 14/028,718, filed Sep. 17, 2013,now U.S. Pat. No. 8,903,212, which is a continuation of application Ser.No. 12/473,931, filed May 28, 2009, now U.S. Pat. No. 8,548,293, whichapplication claims the benefit of provisional application Ser. No.61/056,465, filed May 28, 2008 and provisional application Ser. No.61/109,048, filed Oct. 28, 2008, which applications are incorporatedherein by reference in their entirety.

BACKGROUND

A fiber optic cable typically includes: (1) an optical fiber; (2) abuffer layer that surrounds the optical fiber; (3) a plurality ofstrength members loosely surrounding the buffer layer; and (4) an outerjacket. Optical fibers function to carry optical signals. A typicaloptical fiber includes an inner core surrounded by a cladding that isprotected by a coating. The buffer layer functions to surround andprotect the coated optical fibers. Strength members add mechanicalstrength to fiber optic cables to protect the internal optical fibersagainst stresses applied to the cables during installation andthereafter. Outer jackets also provide protection against chemicaldamages.

The use of strength members that loosely surround the optical fiber cancreate difficulties in manufacturing and/or installing fiber opticcables as these loosely situated strength members can be difficult tocut and difficult to use in automated manufacturing processes.

SUMMARY

An aspect of the present disclosure relates to a fiber optic cablehaving an optical fiber, a strength layer surrounding the optical fiber,and an outer jacket surrounding the strength layer. The strength layerincludes a matrix material in which is integrated a plurality ofreinforcing fibers.

Another aspect of the present disclosure relates to a fiber optic cablehaving an optical fiber, a strength layer surrounding the optical fiber,a first electrical conductor affixed to an outer surface of the strengthlayer, a second electrical conductor affixed to the outer surface of thestrength layer, and an outer jacket surrounding the strength layer. Thestrength layer includes a polymeric material in which is integrated aplurality of reinforcing fibers.

Another aspect of the present disclosure relates to a method ofmanufacturing a fiber optic cable. The method includes mixing a basematerial in an extruder. A strength layer is formed about an opticalfiber. The strength layer includes a polymeric film with integratedreinforcing fibers disposed in the film. The base material is extrudedthrough an extrusion die to form an outer jacket.

A variety of additional aspects will be set forth in the descriptionthat follows. These aspects can relate to individual features and tocombinations of features. It is to be understood that both the foregoinggeneral description and the following detailed description are exemplaryand explanatory only and are not restrictive of the broad concepts uponwhich the embodiments disclosed herein are based.

DRAWINGS

FIG. 1 is a fragmentary perspective view of a fiber optic cable havingfeatures that are examples of aspects in accordance with the principlesof the present disclosure.

FIG. 2 is a perspective view of an optical fiber suitable for use in thefiber optic cable of FIG. 1 .

FIG. 3 is a cross-sectional view of the fiber optic cable of FIG. 1 .

FIG. 4 is perspective view of a pre-formed strength layer of the fiberoptic cable of FIG. 1 .

FIG. 5 is a perspective view of the strength layer of FIG. 4 in agenerally cylindrical shape.

FIG. 6 is a cross-sectional view of an alternate embodiment of astrength layer suitable for use with the fiber optic cable of FIG. 1 .

FIG. 7 is a perspective view of an alternate embodiment of a fiber opticcable having features that are example of aspects in accordance with theprinciples of the present disclosure.

FIG. 8 is a cross-sectional view of the fiber optic cable of FIG. 7 .

FIG. 9 is a cross-sectional view of an embodiment of first and secondelectrical conductors suitable for use with the fiber optic cable ofFIG. 7 .

FIG. 10 is a schematic representation of a tracer light system circuit.

FIG. 11 is a schematic representation of a tracer light system installedon the fiber optic cable of FIG. 7 .

FIG. 12 is a schematic representation of a system for manufacturing thefiber optic cable of FIGS. 1 and 7 in accordance with the principles ofthe present disclosure.

FIG. 13 is a cross-section view of a crosshead suitable for use with thesystem of FIG. 12 .

FIG. 14 is a cross-sectional view of a first example alternateembodiment of a fiber optic cable having aspects in accordance with theprinciples of the present disclosure.

FIG. 15 is a cross-sectional view of a second example alternateembodiment of a fiber optic cable having aspects in accordance with theprinciples of the present disclosure.

FIG. 16 is a cross-sectional view of a third example alternateembodiment of a fiber optic cable having aspects in accordance with theprinciples of the present disclosure.

FIG. 16A is a schematic view of a fiber bundle suitable for use with thefiber optic cable of FIG. 16 .

FIG. 17 is a schematic view of the third example alternate embodiment ofthe fiber optic cable with a connector belonging to a first exampleconnector type.

FIG. 18 is a schematic view of the third example alternate embodiment ofthe fiber optic cable with a connector belonging to a second exampleconnector type.

FIG. 19 is a cross-sectional view of a fourth example alternateembodiment of a fiber optic cable having aspects in accordance with theprinciples of the present disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to the exemplary aspects of thepresent disclosure that are illustrated in the accompanying drawings.Wherever possible, the same reference numbers will be used throughoutthe drawings to refer to the same or like structure.

Referring now to FIG. 1 , a fiber optic cable, generally designated 10,is shown. The fiber optic cable 10 includes at least one optical fiber12, a strength layer 14 surrounding the optical fiber 12, and an outerjacket 18 surrounding the strength layer 14. In the subject embodiment,the fiber optic cable 10 includes a connector 16 disposed at an end ofthe fiber optic cable 10.

Referring now to FIG. 2 , the optical fiber 12 includes a core 20. Thecore 20 is made of a glass material, such as a silica-based material,having an index of refraction. In the subject embodiment, the core 20has an outer diameter D₁ of less than or equal to about 10 μm.

The core 20 of each optical fiber 12 is surrounded by a first claddinglayer 22 that is also made of a glass material, such as a silicabased-material. The first cladding layer 22 has an index of refractionthat is less than the index of refraction of the core 20. Thisdifference between the index of refraction of the first cladding layer22 and the index of refraction of the core 20 allows an optical signalthat is transmitted through the optical fiber 12 to be confined to thecore 20.

A trench layer 24 surrounds the first cladding layer 22. The trenchlayer 24 has an index of refraction that is less than the index ofrefraction of the first cladding layer 22. In the subject embodiment,the trench layer 24 is immediately adjacent to the first cladding layer22.

A second cladding layer 26 surrounds the trench layer 24. The secondcladding layer has an index of refraction. In the subject embodiment,the index of refraction of the second cladding layer 26 is about equalto the index of refraction of the first cladding layer 22. The secondcladding layer 26 is immediately adjacent to the trench layer 24. In thesubject embodiment, the second cladding layer 26 has an outer diameterD₂ of less than or equal to 125 μm.

A coating, generally designated 28, surrounds the second cladding layer26. The coating 28 includes an inner layer 30 and an outer layer 32. Inthe subject embodiment, the inner layer 30 of the coating 28 isimmediately adjacent to the second cladding layer 26 such that the innerlayer 30 surrounds the second cladding layer 26. The inner layer 30 is apolymeric material (e.g., polyvinyl chloride, polyethylenes,polyurethanes, polypropylenes, polyvinylidene fluorides, ethylene vinylacetate, nylon, polyester, or other materials) having a low modulus ofelasticity. The low modulus of elasticity of the inner layer 30functions to protect the optical fiber 12 from microbending.

The outer layer 32 of the coating 28 is a polymeric material having ahigher modulus of elasticity than the inner layer 30. In the subjectembodiment, the outer layer 32 of the coating 28 is immediately adjacentto the inner layer 30 such that the outer layer 32 surrounds the innerlayer 30. The higher modulus of elasticity of the outer layer 32functions to mechanically protect and retain the shape of optical fiber12 during handling. In the subject embodiment, the outer layer 32defines an outer diameter D₃ of less than or equal to 500 μm. In anotherembodiment, the outer layer 32 has an outer diameter D₃ of less than orequal to 250 μm.

In the subject embodiment, the optical fiber 12 is manufactured toreduce the sensitivity of the optical fiber 12 to micro or macro-bending(hereinafter referred to as “bend insensitive”). An exemplary bendinsensitive optical fiber 12 has been described in U.S. Pat. ApplicationPublication Nos. 2007/0127878 and 2007/0280615 and are herebyincorporated by reference in their entirety. An exemplary bendinsensitive optical fiber 12 suitable for use in the fiber optic cable10 of the present disclosure is commercially available from Draka Comtequnder the name BendBright XS.

Referring now to FIGS. 3-5 , the strength layer 14 is a flat andflexible sheet, film, or layer of material that is adapted to surroundthe optical fibers 12. The strength layer 14 is flat in that the widthand the height of the strength layer 14 are generally consistentthroughout the length of the strength layer 14 and in that the width ofthe strength layer 14 is greater than the height of the strength layer14 throughout the length of the strength layer 14. For example, in oneembodiment, the strength layer 14 has a width of 0.12 inches and aheight of 0.030 inches. In other examples, the width of the strengthlayer 14 may be five, ten, or fifteen times as greater than the heightof the strength layer 14. Other proportions of the width of the strengthlayer 14 to the height of strength layer 14 may be possible.

The strength layer 14 includes a binder 34 and a plurality ofreinforcing fibers 36 embedded or otherwise integrated within the binder34. In one example embodiment, the binder 34 is a polymeric materialsuch as ethylene acetate, acrylite (e.g., UV-cured, etc.), silicon(e.g., RTV, etc.), polyester films (e.g., biaxially orientedpolyethylene terephthalate polyester film, etc.), and polyisobutylene.In other example instances, binder 34 may be a matrix material, anadhesive material, a finish material, or another type of material thatbinds, couples, or otherwise mechanically links together reinforcingfibers 36.

The reinforcing fibers 36 are strands that extend the length of thestrength layer 14. It will be understood, however, that the scope of thepresent disclosure is not limited to the reinforcing fibers 36 extendingthe length of the strength layer 14. In one embodiment, the reinforcingfibers 36 are aramid fibers. In another embodiment, the reinforcingfibers 36 are glass fibers, such as E-glass, S-glass, or another type ofglass fiber. The width and height of the strength layer 14 may varydepending on the type of material from which the reinforcing fibers 36are made. For example, when the strength layer 14 is made of E-glass orS-glass, the strength layer 14 may have a width of 0.085 inches and aheight of 0.045 inches. In another example in which the strength layeris made of aramid fibers, the strength layer 14 may have a width of 0.12inches and a height of 0.030 inches. It will be understood that thestrength layer 14 may other widths and heights.

The reinforcing fibers 36 are disposed in a single layer within thebinder 34. It will be understood, however, that the scope of the presentdisclosure is not limited to the reinforcing fibers 36 being disposed ina single layer as the reinforcing fibers 36 could be disposed inmultiple layers. For example, the reinforcing fibers 36 may be disposedin groups. In this example, the reinforcing fibers 36 may be disposed ingroups comprising a variety of different numbers of reinforcing fibers.For instance, each of the groups may comprise 500 reinforcing fibers,1000 reinforcing fibers, 1500 reinforcing fibers, 2000 reinforcingfibers, or other numbers of reinforcing fibers. Furthermore, in someinstances, not all of the groups have the same number of reinforcingfibers.

The binder 34 of the strength layer 14 provides a medium that retainsthe reinforcing fibers 36. The retention of the reinforcing fibers 36 inthe binder 34 is advantageous as the binder 34 with the reinforcingfibers 36 is easier to cut with shears during manufacturing,installation, or repair of the fiber optic cable 10 than cable havingreinforcing fibers that are loosely disposed in the cable. In addition,the manufacturing of fiber optic cable 10 having the binder 34 with thereinforcing fibers 36 is easier to automate than cable having loosereinforcing fibers.

The strength layer 14 includes a first axial end 38, an oppositelydisposed second axial end 40, a first longitudinal edge 42, and a secondlongitudinal edge 44. The strength layer 14 is a flexible layer that iscapable of being bent without breaking. As the sheet of polymericmaterial with the integrated reinforcing members is flexible, thestrength layer 14 is formed into a generally cylindrical shape duringthe manufacturing of the fiber optic cable 10. In the depictedembodiment of FIG. 5 , the strength layer 14 is formed in the generallycylindrical shape by abutting the first and second longitudinal edges42, 44 of the strength layer 14 such that the strength layer 14 definesa longitudinal bore 46. In the subject embodiment, the optical fiber 12is disposed within the longitudinal bore 46.

As best shown in FIG. 5 , the second axial end 40 is rotationallydisplaced from the first axial end 38 about a longitudinal axis 48 ofthe strength layer 14. In the subject embodiment, the strength layer 14is twisted about the longitudinal axis 48 such that the butt jointformed by the abutment of the first and second longitudinal edges 42, 44is helically disposed along the length of the strength layer 14. Thishelical disposition of the butt joint may be advantageous as iteliminates or reduces the risk of a space or gap forming between thefirst longitudinal edge 42 and the second longitudinal edge 44.

Referring now to FIG. 6 , an alternate embodiment of the strength layer14 is shown. In this alternate embodiment, the first longitudinal edge42 overlaps the second longitudinal edge 44. As the overlap of the firstand second longitudinal edges 42, 44 reduces the risk of a space formingbetween the first and second longitudinal edges 42, 44, the first andsecond axial ends 38, 40 are not rotationally offset in this alternateembodiment.

Referring now to FIGS. 1 and 3 , the outer jacket 18 of the fiber opticcable 10 surrounds the strength layer 14. The outer jacket 18 includes abase material that is a thermoplastic material. In one embodiment, thebase material is a low-smoke zero halogen material such as low-smokezero halogen polyolefin and polycarbonate. In another embodiment, thebase material is a conventional thermoplastic material such aspolyethylene, polypropylene, ethylene-propylene, copolymers, polystyreneand styrene copolymers, polyvinyl chloride, polyamide (nylon),polyesters such as polyethylene terephthalate, polyetheretherketone,polyphenylene sulfide, polyetherimide, polybutylene terephthalate, aswell as other thermoplastic materials.

In one embodiment, an inner diameter of the outer jacket 18 is bonded tothe strength layer 14. This bonding of the inner diameter of the outerjacket 18 and the strength layer 14 can be chemical bonding or thermalbonding. For example, the strength layer 14 may be coated with ethyleneacetate to bond the strength layer 14 to the outer jacket 18. In anotherembodiment, the inner diameter of the outer jacket 18 is not bonded tothe strength layer 14.

In the subject embodiment, the outer jacket 18 has an outer diameterthat is less than or equal to about 4 mm. In another embodiment, theouter jacket 18 has an outer diameter that is less than or equal toabout 3.0 mm. In another embodiment, the outer jacket 18 has an outerdiameter that is less or equal to about 2.0 mm. In another embodiment,the outer jacket 18 has an outer diameter that is less than or equal toabout 1.6 mm. In another embodiment, the outer jacket 18 has an outerdiameter that is less than or equal to about 1.2 mm.

In one embodiment, the outer jacket 18 includes shrinkage reductionmaterial disposed in the base material. The shrinkage reduction materialin the base material of the outer jacket 18 is adapted to resistpost-extrusion shrinkage. U.S. patent application Ser. No. 11/039,122now U.S. Pat. No. 7,379,642 describes an exemplary use of shrinkagereduction material in the base material of the outer jacket and ishereby incorporated by reference in its entirety.

In one embodiment, the shrinkage reduction material is liquid crystalpolymer (LCP). Examples of liquid crystal polymers suitable for use inthe fiber optic cable 10 are described in U.S. Pat. Nos. 3,991,014;4,067,852; 4,083,829; 4,130,545; 4,161,470; 4,318,842; and 4,468,364 andare hereby incorporated by reference in their entireties.

In order to promote flexibility in the fiber optic cable 10, theconcentration of shrinkage reduction material is relatively small ascompared to the base material. In one embodiment, and by way of exampleonly, the shrinkage reduction material constitutes less than about 10%of the total weight of the outer jacket 18. In another embodiment, andby way of example only, the shrinkage reduction material constitutesless than about 5% of the total weight of the outer jacket 18. Inanother embodiment, the shrinkage reduction material constitutes lessthan about 2% of the total weight of the outer jacket 18. In anotherembodiment, the shrinkage reduction material constitutes less than about1.9%, less than about 1.8%, less than about 1.7%, less than about 1.6%,less than about 1.5%, less than about 1.4%, less than about 1.3%, lessthan about 1.2%, less than about 1.1%, or less than about 1% of thetotal weight of the outer jacket 18.

Referring now to FIGS. 7 and 8 , an alternate embodiment of a fiberoptic cable assembly, generally designated 50, is shown. In thisalternate embodiment, the fiber optic cable assembly 50 includes theoptical fiber 12, the strength layer 14, and the outer jacket 18.

In the subject embodiment, the strength layer 14 includes an outersurface 52. First and second electrical conductors 54, 56 are oppositelymounted to the outer surface 52 of the strength layer 14 and extend thelength of the strength layer 14 between the first and second axial ends38, 40 (shown in FIGS. 4 and 5 ). The first and second electricalconductors 54, 56 are spaced apart (e.g., circumferentiallyspaced-apart) about the outer surface 52 of the strength layer 14 suchthat first electrical conductor 54 is not in electrical communicationwith the second electrical conductor 56. In the subject embodiment, thefirst and second electrical conductors 54, 56 are disposed about 180degrees apart.

In one embodiment, the first and second electrical conductors 54, 56 areformed from conductive tape (e.g., metalized polyester tape, metalizedMYLAR® tape, etc.). In one embodiment, the conductive tape has a widththat is larger than the thickness of the conductive tape. In oneembodiment, the conductive tape includes an adhesive surface 58 and anoppositely disposed conductive surface 60. The adhesive surface 58 isaffixed to the outer surface 52 of the strength layer 14.

In the depicted embodiments of FIGS. 7-8 , the first and secondelectrical conductors 54, 56 are made from separate strips of conductivetape. In the depicted embodiment of FIG. 9 , the first and secondelectrical conductors are formed from conductive tape having a firstsurface 62 and an oppositely disposed second surface 64. The firstsurface 62 includes an adhesive for affixing the conductive tape to theouter surface 52 of the strength layer 14. The second surface 64includes first and second conductive strips 66 a, 66 b. The first andsecond conductive strips 66 a, 66 b are separated such that the firstconductive strip 66 a is not in electrical communication with the secondconductive strip 66 b. In the depicted embodiment of FIG. 9 , the firstconductive strip 66 a is disposed adjacent to a first side 68 of themetalized tape while the second conductive strip 66 b is disposedadjacent to a second side 70. In the subject embodiment, the width ofthe conductive tape is sized so that the first and second conductivestrips 66 a, 66 b are disposed about 180 degrees apart when theconductive tape is affixed to the strength layer 14.

Referring now to FIGS. 10 and 11 , a schematic representation of atracer light system, generally designated 100, is shown. The tracerlight system 100 can be used to identify an end of an individual fiberoptic cable 50 when multiple fiber optic cables 50 are being routedthrough a particular location. The tracer light system 100 includes apower source 102, first and second tracer lights 104 a, 104 b,respectively, and first and second contacts 106 a, 106 b, respectively.

In the subject embodiment, the power source 102 is a device includingmating contacts 108 that are adapted for electrical communication withone of the first and second contacts 106 a, 106 b. In the subjectembodiment, the power source 102 further includes a battery (e.g.,alkaline, nickel-cadmium, nickel-metal hydride, etc.).

In the depicted embodiment of FIG. 11 , the first and second tracerlights 104 a, 104 b and the first and second contacts 106 a, 106 b aredisposed in first and second housings 110 a, 110 b, respectively. Eachof the first and second housings 110 a, 110 b is engaged with the fiberoptic cable 50. In the subject embodiment, the first housing 110 a isdisposed at one end of the fiber optic cable 50 while the second housing110 b is disposed at an opposite end of the fiber optic cable 50.

Each of the first and second tracer lights 104 a, 104 b includes anillumination source (e.g., a light-emitting diode (LED), etc.). In thesubject embodiment, the first tracer light 104 a is in electricalcommunication with the first and second electrical conductors 54, 56 ofthe fiber optic cable 50 and the first contacts 106 a while the secondtracer light 104 b is in electrical communication with the first andsecond electrical conductors 54, 56 and the second contacts 106 b.

In operation, the mating contacts 108 of the power source 102 are placedelectrical communication with one of the first and second contacts 106a, 106 b in one of the first and second housings 110 a, 110 b of thefiber optic cable 50. With power supplied to the first and secondelectrical conductors 54, 56 through one of the first and secondcontacts 106 a, 106 b, the first and second tracer lights 104 a, 104 bon the fiber optic cable 50 illuminate. With the first and second tracerlights 104 a, 104 b of the fiber optic cable 50 illuminated, thecorresponding end of the fiber optic cable 50 can be quickly identified.

Referring now to FIG. 12 , a schematic representation of a system 200for making the fiber optic cable 50 is shown. The system 200 includes acrosshead, generally designated 202, that receives thermoplasticmaterial from an extruder 204. A hopper 206 is used to feed materialsinto the extruder 204. A first conveyor 208 conveys the base material tothe hopper 206. In an embodiment in which the fiber optic cable 50includes shrinkage reduction material integrated within the outer jacket18, a second conveyor 210 is used to convey the shrinkage reductionmaterial to the hopper 206. The extruder 204 is heated by a heatingsystem 212 that may include one or more heating elements for heatingzones of the extruder 204 as well as the crosshead 202 to desiredprocessing temperatures. The optical fiber 12 is fed into the crosshead202 from a feed roll 214.

An application assembly 216 is used to apply the strength layer 14 tothe optical fiber 12. The application assembly 216 includes a firstsupply roll 218 and a longitudinal folding tool 220. The strength layer14 is disposed on the first supply roll 218. In one embodiment, thestrength layer 14, which is disposed on the first supply roll 218,includes the first and second electrical conductors 54, 56 affixed tothe outer surface 52 of the strength layer 14.

The longitudinal folding tool 220 is used to form the generallycylindrical shape of the strength layer 14. In the subject embodiment,as the optical fiber 12 passes the first supply roll 218, the strengthlayer 14 disposed on the first supply roll 218 is paid out or dispensed.The strength layer 14 enters the longitudinal folding tool 220 where thestrength layer 14 is formed into the cylindrical shape about the opticalfiber 12 and applied around the optical fiber 12.

A water trough 222 is located downstream from the crosshead 202 forcooling the extruded product that exits the crosshead 202. The cooledfinal product is stored on a take-up roll 224 rotated by a drivemechanism 226. A controller 228 coordinates the operation of the variouscomponents of the system 200.

In one embodiment, the feed roll 214 and the take-up roll 224 remainstationary while the first supply roll 218 and the longitudinal foldingtool 220 rotate in a direction 230 (shown as a dashed arrow in FIG. 12 )about the optical fiber 12 so that the strength layer 14 is helicallywrapped about the longitudinal axis 48. In this embodiment, the feedroll 214 and the take-up roll 224 are held stationary so that theoptical fiber 12 does not get twisted. In another embodiment, the feedroll 214, the take-up roll 224 and the longitudinal folding tool 220remain stationary while the first supply roll 218 rotates in thedirection 230.

In an alternate embodiment, the first supply roll 218 and thelongitudinal folding tool 220 remain stationary while the feed roll 214and the take-up roll 224 rotate in the direction 230. In this alternateembodiment, the feed roll 214 and the take-up roll 224 rotate at thesame speed and in the same direction so that the optical fiber 12 doesnot get twisted.

In use of the system 200, the base material and the shrinkage reductionmaterial for the outer jacket 18 are delivered to the hopper 206 by thefirst and second conveyors 208, 210, respectively. The controller 228preferably controls the proportions of the base material and theshrinkage reduction material delivered to the hopper 206. In oneembodiment, the shrinkage reduction material constitutes less than 2% byweight of the total material delivered to the hopper 206. In anotherembodiment, the shrinkage reduction material constitutes less than about1.4% by weight.

From the hopper 206, the material moves by gravity into the extruder204. In the extruder 204, the material is mixed, masticated, and heated.In one embodiment, the material is heated to a temperature greater thanthe melting temperature of the base material, but less than the meltingtemperature of the shrinkage reduction material. The temperature ispreferably sufficiently high to soften the shrinkage reduction materialsuch that the shrinkage reduction material is workable and extrudable.The extruder 204 is heated by the heating system 212. The extruder 204also functions to convey the material to the crosshead 202, and toprovide pressure for forcing the material through the crosshead 202.

Referring now to FIG. 13 , the extruder 204 is depicted as including anextruder barrel 240 and an auger-style extruder screw 242 positionedwithin the extruder barrel 240. An extruder screen 244 can be providedat the exit end of the extruder 204. The extruder screen 244 preventspieces too large for extrusion from passing from the extruder into thecrosshead 202.

The crosshead 202 includes a jacket material input location 300 thatreceives thermoplastic material from the extruder 204. The crosshead 202also includes a tip 302 and a die 304. The tip 302 defines an innerpassageway 306 through which the optical fiber 12 and the strength layer14 are fed. The die 304 defines an annular extrusion passage 308 thatsurrounds the exterior of the tip 302. The crosshead 202 defines anannular passageway for feeding the thermoplastic material to the annularextrusion passage 308. Within the crosshead 202, the flow direction ofthe thermoplastic material turns 90 degrees relative to the flowdirection of the extruder 204 to align with the bundled fiber.

Within the crosshead 202, the material provided by the extruder 204 ispreferably maintained at a temperature greater than the melt temperatureof the base material of the outer jacket 18, but less than the melttemperature of the shrinkage reduction material. In one embodiment, thetemperature of the thermoplastic material is high enough to thermallybond the thermoplastic material to the binder 34 of the strength layer14 as the thermoplastic material is extruded. The extruded fiber opticcable 10 is then cooled and shape set at the water trough 222. Theextrusion process can be a pressure or semi-pressure extrusion processwhere product leaves the crosshead 202 at the desired shape, or anannular extrusion process where the product is drawn down afterextrusion. After cooling, the product is collected on the take-up roll224.

Referring now to FIG. 14 , a transverse cross-sectional view of anotherfiber optic cable 410 having features in accordance with the principlesof the present disclosure is shown. The fiber optic cable 410 includes aplurality of optical fibers 412, a strength layer 414 positioned outsideand at least partially around the optical fibers 412, and an outerjacket 418. The outer jacket 418 surrounds the optical fibers 412 andthe strength layer 414 is imbedded within the outer jacket 418.

In the depicted embodiment of FIG. 14 , the fiber optic cable 410 isprovided with twelve of the optical fibers 412. It will be appreciatedthat the optical fibers 412 can have the same construction as theoptical fiber 12 described with respect to the embodiment of FIG. 1 . Inone embodiment, the fiber optic cable 410 includes at least one opticalfiber 412. In another embodiment, the fiber optic cable 410 includes 1to 24 optical fibers 410. In another embodiment, the fiber optic cable410 includes at least 12 optical fibers 410.

The outer jacket 418 is shown having a non-circular transversecross-sectional shape. For example, the outer jacket 418 is shown havingan outer profile that is elongated in a first direction as compared to aperpendicular second direction. For example, the outer jacket 418 isshown having a longer dimension L₁ along a major axis 419 as compared toa dimension L₂ that extends along a minor axis 421 of the outer jacket418. As depicted in FIG. 14 , the outer jacket 418 has a generallyrectangular or oblong outer profile.

It will be appreciated that the outer jacket 418 can be manufactured ofa variety of different polymeric materials. In one embodiment, the outerjacket 418 is made of a low density polyethylene material. In anotherembodiment, the outer jacket 418 is made of a medium densitypolyethylene material. In another embodiment, the outer jacket 418 ismade of a high density polyethylene material. In one embodiment, theouter jacket 418 is made of a low density ultra-high molecular weightpolyethylene material. In another embodiment, the outer jacket 418 ismade of a medium density ultra-high molecular weight polyethylenematerial. In another embodiment, the outer jacket 418 is made of a highdensity ultra-high molecular weight polyethylene material. In thedepicted embodiment, the outer jacket 418 defines a central channel 422in which the optical fibers 412 are located. It will be appreciate thatthe optical fibers 412 can be contained within one or more buffer tubespositioned within the channel 422. For example, in one embodiment, theoptical fibers 412 can be provided in one large buffer tube that linesthe channel 422 of the outer jacket 418. In other embodiments, theoptical fibers 412 can be positioned directly within the channel 422without any intermediate tubes or layers positioned between the opticalfibers 412 and the material of the outer jacket 418 that defines thechannel 422. In such embodiment, the outer jacket 418 itself functionsas a buffer tube.

To prevent water from migrating along the channel 422, structures can beprovided within the channel 422 for absorbing water or otherwiseblocking water flow along the length of the channel 422. For example,water blocking gel can be provided within the channel 422. In otherembodiments, water-swellable fibers, tape or thread can be providedwithin the channel 422.

Referring still to FIG. 14 , the strength layer 414 is shown includingtwo flat and flexible sheets or films that are embedded or otherwiseposition within the outer jacket 418. The flat and flexible sheets orfilms can have the same construction as the strength layer 14 describedwith respect to FIGS. 3-5 . For example, each of the flexible sheets orfilms can include a matrix material in which a plurality of reinforcingfibers are embedded or otherwise integrated. The sheets or films areshown positioned on opposite sides of the minor axis 421 of the outerjacket 418. The flexible sheets or films are also shown on oppositesides of the channel 422 and are shown having a curvature that generallymatches the curvature of the outer channel. It will be appreciated thatthe sheets or films provide axial reinforcement to the outer jacket 418.

FIG. 15 shows a second alternative fiber optic cable 410′ having thesame general design as the fiber optic cable 410. The second alternativefiber optic cable 410′ has a modified strength layer 414′ having asingle sheet or film that fully circumferentially surrounds the channel422 of the outer jacket 418. Additionally, the channel 422 of the outerjacket 418 is shown lined with a buffer tube 430.

It will be appreciated that the cables of FIGS. 14 and 15 can be used asdrop cables in a fiber optic network. For example, the fiber opticcables 410, 410′ can be used as drop cables in fiber optic networks suchas the networks disclosed in U.S. Provisional patent application Ser.No. 61/098,494, which is entitled “Methods and Systems for DistributingFiber Optic Telecommunications Services to a Local Area,” filed on Sep.19, 2008 and hereby incorporated by reference in its entirety.

FIG. 16 is a cross-sectional view of a third example alternateembodiment of a fiber optic cable 500 from an axial perspective. Asillustrated in the example of FIG. 16 , fiber optic cable 500 includes aplurality of optical fibers 502, a first strength layer 504A, a secondstrength layer 504B, and an outer jacket 506. This disclosure refers tothe strength layer 504A and the strength layer 504B collectively asstrength layers 504. The outer jacket 506 defines a channel 508 withinwhich the optical fibers 502 are disposed. The strength layer 504A andthe strength layer 504B are embedded within the outer jacket 506. In oneexample, the strength layers 504 are coated with ethylene acetate tobond the strength layers 504 to the outer jacket 506. Each of strengthlayers 504 can have the same construction as the strength layer 14described above.

In the example embodiment depicted in FIG. 16 , the fiber optic cable500 is provided with twelve of the optical fibers 502. It will beappreciated that the optical fibers 502 can have the same constructionas the optical fiber 12 described with respect to the example of FIG. 1. Furthermore, it will be appreciated that in other examples, the fiberoptic cable 500 may include more than twelve optical fibers or fewerthan twelve optical fibers. For example, in one embodiment, the fiberoptic cable 500 may include twenty four optical fibers 502.

Referring now to FIG. 16A, a fiber bundle 505 is shown. The fiber bundle505 includes a plurality of optical fibers 502. The plurality of opticalfibers 502 is held together by a plurality of strength members 507. Inthe depicted embodiment of FIG. 16A, only two strength members 507 areshown for ease of illustration purposes only.

The strength members 507 are disposed in two sets about the opticalfibers 502. In the subject embodiment, the strength members 507 includea first set of strength members 507 a and a second set of strengthmembers 507 b. The second set of strength members 507 b is disposed overthe first set of strength members 507 a such that the first and secondsets of strength members 507 a, 507 b are unbraided or nonwoven.

In the subject embodiment, the first and second sets of strength members507 a, 507 b are contra-helically served. For example, in the depictedembodiment of FIG. 16A, the first set of strength members 507 a isdisposed about the optical fibers 502 in a generally right-handedhelical configuration while the second set of strength members 507 b isdisposed over the first set of strength members 507 a in a generallyleft-handed helical configuration. The first and second sets of strengthmembers 507 a, 507 b are disposed at angles α₁, α₂ from a longitudinalline 509. In one embodiment, the angles α₁, α₂ are equal but opposite.In another embodiment, the angles α₁, α₂ are in the range of about 0.1degrees to about 20 degrees. In another embodiment, the angles α₁, α₂are in the range of about 5 degrees to about 20 degrees. In anotherembodiment, the angles α₁, α₂ are in the range of about 0.1 degrees toabout 15 degrees. In another embodiment, the angles α₁, α₂ are in arange of about 1 degree to about 15 degrees. In another embodiment, theangles α₁, α₂ are in the range of about 5 degrees to about 15 degrees.In another embodiment, the angles α₁, α₂ are in a range of about 0.1degrees to about 5 degrees. In another embodiment, the angles α₁, α₂ arein a range of about 0.1 degrees to about 1 degree.

In the subject embodiment, each of the strength members 507 has a laylength in a range of about 3 inches to about 18 inches. The lay lengthis the axial distance in which each of the strength members 507 wraps360° around the plurality of optical fibers 502.

In one embodiment, the strength members 507 are strands of aramid yarn.In another embodiment, the strength members 507 are water swellableyarns. In one embodiment, there are one to ten strength members 507 inthe first set of strength members 507 a and one to ten strength members507 in the second set of strength members 507 b. In another embodiment,there are one to eight strength members 507 in the first set of strengthmembers 507 a and one to eight strength members 507 in the second set ofstrength members 507 b. In another embodiment, there are four strengthmembers 507 in the first set of strength members 507 a and four strengthmembers 507 in the second set of strength members 507 b.

Referring again to FIG. 16 , the fiber optic cable 500 has anon-circular transverse cross-sectional shape. In the example of FIG. 16, the outer jacket 506 has a longer dimension L₁ along a major axis 510of the outer jacket 506 as compared to a dimension L₂ that extends alonga minor axis 512 of the outer jacket 506. As depicted in FIG. 16 , theouter jacket 506 has a generally rectangular or oblong outer profile.The major axis 510 and the minor axis 512 intersect perpendicularly at alengthwise axis 511 of the fiber optic cable 500.

As viewed in the example of FIG. 16 , the width of outer jacket 506 maybe divided lengthwise into three portions: a first portion 524 to theleft of the left side of the channel 508, a second portion 526 betweenthe left side of the channel 508 and a right side of the channel 508,and a third portion 528 to the right of the right side of the channel508. The first portion 524 and the third portion 528 are solidthroughout. Consequently, the first portion 524 and the third portion528 of the outer jacket 506 prevent the outer jacket 506 fromcompressing inward onto the channel 508 when a clamp or other structureis used to retain the fiber optic cable 500. Because the outer jacket506 does not compress inward onto the channel 508, the optical fibers502 are not crushed when the clamp is used to retain the fiber opticcable 500.

The strength layers 504 have height (h), width (w), and lengthdimensions. The length dimensions of the strength layers 504 are alignedalong a lengthwise axis 511 of the fiber optic cable 500. A top surface514A of the strength layer 504A and a bottom surface 516A of thestrength layer 504A are aligned parallel to the major axis 510. Sidesurfaces 518A of the strength layer 504A are aligned parallel to theminor axis 512. The top surface 514A and the bottom surface 516A arewider along the major axis 510 than the height of the side surfaces 518Aalong the minor axis 512. Similarly, a top surface 514B of the strengthlayer 504B and a bottom surface 516B of the strength layer 504B arealigned parallel to the major axis 510. Side surfaces 518B of thestrength layer 504B are aligned parallel to the minor axis 512. The topsurface 514B and the bottom surface 516B are wider along the major axis510 than the height of the side surfaces 518B along the minor axis 512.

The strength layers 504 are aligned along the major axis 510 such thatthe major axis 510 bisects the heights h of the strength layers 504. Themajor axis 510 is generally parallel to the widths w of the strengthlayers 504. As used in this disclosure, “generally parallel” meansparallel or almost parallel. The strength layers 504 can include aplurality of strength members held together in a flat configuration by abinder. For example, the strength layers 504 can have the sameconstruction as the strength layer 14 previously discussed herein.

The top surface 514A of the strength layer 504A is a consistent distancefrom a top surface 520 of the outer jacket 506 and the bottom surface516A is a consistent distance from a bottom surface 522 of the outerjacket 506. Similarly, the top surface 514B of the strength layer 504Bis a consistent distance from the top surface 520 of the outer jacket506 and the bottom surface 516B is a consistent distance from the bottomsurface 522 of the outer jacket 506. Because of this alignment of thestrength layers 504 within the outer jacket 506, it may be possible tospool the fiber optic cable 500 in a relatively tight diameter.

FIG. 17 is a schematic view that illustrates an example technology toattach the fiber optic cable 500 with a connector 550 belonging to afirst example connector type. In the example of FIG. 17 , the strengthlayers 504 of the fiber optic cable 500 and the channel 508 of the fiberoptic cable 500 are shown. Other details of the fiber optic cable 500are omitted for clarity.

Although not visible in the example of FIG. 17 due to perspective, theconnector 550 is shaped to define a recess into which an end of thefiber optic cable 500 can be inserted. Furthermore, the connector 550includes a ferrule 551 that serves to align the optical fibers 502 withcorresponding optical fibers in a separate connector. In the example ofFIG. 17 , ends 552 of the optical fibers 502 are shown.

In preparation to attach connector 550 to the fiber optic cable 500,holes 554A and 554B are formed in the fiber optic cable 500. In thecurrent disclosure, the hole 554A and the hole 554B are collectivelyreferred to as “holes 554.” The holes 554 may be formed in a variety ofways. For example, the holes 554 may be formed by drilling, melting,puncturing, punching, or some other process. The hole 554A extendstransversely through the outer jacket 506 of the fiber optic cable 500and through the strength layer 504A of the fiber optic cable 500. Thehole 554B extends transversely through the outer jacket 506 and thestrength layer 504B.

A hole 556A and a hole 556B are defined in the connector 550. In thecurrent disclosure, the hole 556A and the hole 556B are collectivelyreferred to as “holes 556.” Holes 556 extend transversely through theconnector 550. Holes 556 may have approximately the same diameter asholes 554 and are defined in the connector 550 such that, when the fiberoptic cable 500 is inserted into the connector 550, the holes 556 arealigned with the holes 554 in the fiber optic cable 500.

When the fiber optic cable 500 is inserted into the connector 550, aretention member 558A can be inserted through the hole 556A in theconnector 550 and the hole 554A in the fiber optic cable 500. Likewise,a retention member 558B can be inserted through the hole 556B in theconnector 550 and the hole 554B in the fiber optic cable 500. In thecurrent disclosure, the retention member 558A and the retention member558B are collectively referred to as “retention members 558.” Theretention members 558 may have diameters that are approximately the samediameter as the diameters of the holes 554 and the holes 556. Retentionmembers 558 may be a variety of different types of retention membersincluding pins, holders, retainers, clips, screws, rivets, bolts,latches, clasps, hooks, pegs, and other types of retention members.

When the retention members 558 are inserted through the holes 554 andthe holes 556, the retention members 558 pass through the strengthlayers 504. Furthermore, after the retention members 558 are insertedthrough the holes 554 and the holes 556, the retention members 558 canbe secured in position using a variety of techniques including taping,gluing, bonding, friction fit, melting, or another technique. In thisway, the retention members 558 secure the connector 550 to the fiberoptic cable 500.

It will be appreciated that FIG. 17 is merely an example. Othertechnologies for connecting the fiber optic cable 500 to the connector550 may have many different variations. For instance, retention members558, holes 554, and holes 556 may be square, round, or other shapes.

FIG. 18 is a schematic view of the third example alternate embodiment ofthe fiber optic cable 500 with a connector 600 belonging to a secondconnector type. The fiber optic cable 500 has the same construction asthe fiber optic cable 500 illustrated in the example of FIG. 16 and FIG.17 .

In the example of FIG. 18 , the fiber optic cable 500 has a hole 602Aand a hole 602B (collectively, “holes 602”). The holes 602 in the fiberoptic cable 500 may be formed in a variety of ways. For example, theholes 602 may be formed by drilling, melting, punching, puncturing, orsome other process. The hole 602A extends transversely through the outerjacket 506 of the fiber optic cable 500 and through the strength layer504A of the fiber optic cable 500. The hole 602A extends transverselythrough the outer jacket 506 and the strength layer 504B.

The connector 600 is split into a first piece 604 and a second piece606. Retaining members 616A and 616B (collectively, “retaining members616”) are integrated into the first piece 604 such that the retainingmembers 616 extend into a recess defined by the first piece 604 and thesecond piece 606. The retaining members 616 may be a variety ofdifferent types of retaining members including pegs, pins, screws,clips, rivets, and other types of retaining members.

The first piece 604 and the second piece 606 may be constructed suchthat the first piece 604 and the second piece 606 may be separated suchthat the fiber optic cable 500 may be inserted into the recess definedby the first piece 604 and the second piece 606. After the fiber opticcable 500 is inserted into the recess defined by the first piece 604 andthe second piece 606, the first piece 604 and the second piece 606 maybe repositioned such that an inner surface 608 of the first piece 604 isin contact with a top surface 610 of the fiber optic cable 500 and aninner surface 612 of the second piece 606 is in contact with a bottomsurface 614 of the fiber optic cable 500.

When the first piece 604 and the second piece 606 are repositioned inthis way, the retaining members 616 are disposed within correspondingholes 602 in the fiber optic cable 500. In other words, the retainingmembers 616 extend through the outer jacket 506 and the strength layers504 of the fiber optic cable 500. In this way, the retaining members 616act to retain the fiber optic cable 500 within the connector 600.

Although not visible in the example of FIG. 18 due to perspective, theconnector 600 includes a ferrule. When the fiber optic cable 500 isinserted into the recess defined by the first piece 604 and the secondpiece 606, the ferrule serves to align the optical fibers of the fiberoptic cable 500 with corresponding optical fibers in a separateconnector.

FIG. 19 is a cross-sectional view of a fourth example alternateembodiment of a fiber optic cable 700. The fiber optic cable 700includes a plurality of optical fibers 702, a strength layer 704, and anouter jacket 706. The outer jacket 706 defines a channel 708 withinwhich the optical fibers 502 are disposed. The strength layer 704 isembedded within the outer jacket 706. In one example, the strength layer704 is coated with ethylene acetate to bond the strength layer 704 tothe outer jacket 706. In one example, the strength layer 704 has thesame construction as the strength layer 14 previously discussed herein.

It should be noted that the fiber optic cable 700 includes one strengthlayer, as opposed to the two strength layers in the fiber optic cable500 illustrated in the example of FIG. 16 . Fiber optic cables thatinclude a single strength layer, as opposed to two or more strengthlayers, may be less expensive to manufacture.

In the example embodiment depicted in FIG. 19 , the fiber optic cable700 is provided with twelve of the optical fibers 702. It will beappreciated that the optical fibers 702 can have the same constructionas the optical fiber 12 described with respect to the example of FIG. 2. Furthermore, it will be appreciated that in other examples, the fiberoptic cable 700 may include more than twelve optical fibers or fewerthan twelve optical fibers.

The fiber optic cable 700 has a non-circular transverse cross-sectionalshape. In the example of FIG. 19 , the outer jacket 706 has a longerdimension L₁ along a major axis 710 of the outer jacket 706 as comparedto a dimension L₂ that extends along a minor axis 712 of the outerjacket 706. The major axis 710 and the minor axis 712 intersectperpendicularly at a lengthwise axis 711 of the fiber optic cable 700.As depicted in FIG. 19 , the outer jacket 706 has a generallyrectangular or oblong outer profile.

The strength layer 704 has a height (h), a width (w), and a lengthdimension. The length dimension of the strength layer 704 is alignedalong the lengthwise axis 711 of the fiber optic cable 700. A topsurface 714 of the strength layer 704 and a bottom surface 716 of thestrength layer 704 are aligned parallel to the major axis 710. Sidesurfaces 718 of the strength layer 704 are aligned parallel to the minoraxis 712. The top surface 714 and the bottom surface 716 are wider alongthe major axis 710 than the height of the side surfaces 718 along theminor axis 712. The strength layer 704 is aligned along the major axis710 such that the major axis 710 bisects the height h of the strengthlayer 704 and is generally parallel to the width w of the strength layer704.

Various modifications and alterations of this disclosure will becomeapparent to those skilled in the art without departing from the scopeand spirit of this disclosure, and it should be understood that thescope of this disclosure is not to be unduly limited to the illustrativeembodiments set forth herein.

What is claimed is:
 1. (canceled)
 2. A fiber optic cable comprising: anoptical fiber; an outer jacket surrounding the optical fiber, the outerjacket defining a channel disposed at a lengthwise axis of the outerjacket through which the optical fiber passes, the outer jacketcomprising a first portion disposed on a first side of the channel and asecond portion disposed on an opposite side of the channel; and astrength layer disposed in the first portion spaced apart from thechannel, wherein the second portion does not contain a strength layer.3. The fiber optic cable of claim 2, wherein the outer jacket is wideralong a major axis of the outer jacket than along a minor axis of theouter jacket, and wherein the major axis and the minor axis intersectperpendicularly at the lengthwise axis of the outer jacket.
 4. The fiberoptic cable of claim 3, wherein the strength layer has a heightdimension, a width dimension and a length dimension; the lengthdimension is aligned along the lengthwise axis of the outer jacket; thewidth dimension is greater than the height dimension; and the widthdimension extends parallel to the major axis of the outer jacket.
 5. Thefiber optic cable of claim 4, wherein the strength layer has a topsurface and a bottom surface; and the top surface and the bottom surfaceare aligned parallel to the major axis of the outer jacket.
 6. The fiberoptic cable of claim 5, wherein the strength layer has opposing sidesurfaces; and the side surfaces are aligned parallel to the minor axisof the outer jacket.
 7. The fiber optic cable of claim 4, wherein theheight dimension extends parallel to the minor axis of the outer jacket,and wherein the major axis bisects the height dimension of the first andsecond strength layers.
 8. The fiber optic cable of claim 2, wherein thestrength layer has a rectangular cross section.
 9. The fiber optic cableof claim 2, further comprising a plurality of optical fibers includingthe optical fiber, wherein the plurality of optical fibers are disposedin the channel.
 10. The fiber optic cable of claim 2, wherein thestrength layer is coated with ethylene acetate.
 11. The fiber opticcable of claim 2, wherein the optical fiber is a bend insensitiveoptical fiber.